Powered appliances, such as cooking ovens, furnaces, and water heaters, washing machines, etc., incorporate motorized mechanisms such as motorized door latches, motorized gas valves, and other motorized devices that communicate and collaborate with the appliance's electronic controls. These motorized devices typically have sensing switches that sense a rotational or linear position of the motorized mechanism. These switches, when actuated, simply communicate open or closed circuits to the appliance controller. These switches are typically arranged radially around a radial cam that is driven by the motor shaft. Other devices incorporate a secondary linear cam or plunger that may be actuated by an appliance door or similar actuation method. This secondary cam or plunger actuates an independent switch that also communicates with the appliance controller. Typically, the controller will not proceed with appliance functions until the secondary switch is actuated by the closing of an appliance door or similar function. Upon actuation of the switch, these motorized mechanisms signal the controller, by opening or closing a circuit, to proceed with the appliance function. As the motor runs, a radial cam on the motor shaft actuates one or more switches in correspondence with the cam's rotational position. Each switch performs a specific sensing function for position of the mechanism. The controller reads the open or closed status of each circuit and operates the mechanism, and other appliance functions, as its programming logic directs.
Due to the radial arrangements of the switches on such mechanisms, wiring connection points are typically physically segregated. Most of these systems have two to five segregated wiring connections points for switches in addition to separate wiring connection points for the motor and the linear cam or plunger actuated switch. Multiple and segregated wiring connection points can be problematic for manufacturers and in-field service technicians. Two known problems include, but are not limited to, considerable assembly time and improper connections. The consequence of improper connections can result in product failure and/or unsafe product operation, all of which are costly for the manufacturer.
One additional problem of these motorized mechanisms is the stack-up of dimensional tolerances in the radial and angular positional relationship of the cam and the switches. This is due to the switches being mounted to adjacent brackets; each of which has independent dimensional tolerances. As these tolerances combine with each other, the accuracy of the sensing function of each switch decreases. Consequently, manufacturers are challenged with producing multiple parts with very small tolerances. This too, is costly for the manufacturer.
In recent years, motorized mechanisms have been developed that incorporate rigid or flexible circuit boards that are directly soldered to the switches and motor. Through a series of circuit paths in the circuit board, these mechanisms provide a single point wiring connection for the motorized device to communicate with the appliance controller. The benefit of such a system is the circuit board fundamentally precludes any possibility of improper connection and the single point wiring connection provides for speedy assembly time. However, circuit boards add cost to the motorized mechanism and add a number of solder connections in direct proportion to the number of switches. Inherently, as solder connections increase, failure mode possibilities also increase. What is needed for motorized mechanisms is a single point wiring connection for switches and motor without the complexity, cost, and solder connections of rigid or flexible circuit boards and without the stack up of tolerances in the radial and angular positional relationship of the cam and switches.